Subject: [AVTCORE] [Technical Errata Reported] RFC4867 (4348)

From: RFC Errata System <[email-masked]>
Date: Mon, 27 Apr 2015 08:48:13 -0700 (PDT)

The following errata report has been submitted for RFC4867,
"RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs".

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You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=4867&eid=4348

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Type: Technical
Reported by: Thomas Belling <[email-masked]>

Section: 4.3.1

Original Text
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   The encoder SHOULD follow a received codec mode request, but MAY
   change to a lower-numbered mode if it so chooses, for example, to
   control congestion.

Corrected Text
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   The encoder MUST follow a received codec mode request as soon as
   possible. It SHOULD use the requested mode, but MAY change to a
   lower-numbered mode if it so chooses, for example, to
   control congestion. However, the encoder MUST NOT use a
   higher-numbered mode than the received codec mode request.

Notes
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This seems to be the intention of the existing text, but is not explicitly stated. It is essential for the end-to-end mode control and interoperability with 3GPP CS networks that a peer does not send higher modes than requested.

This erratum has been discussed and endorsed by the 3GPP SA4 group before submission to IETF.

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RFC4867 (draft-ietf-avt-rtp-amr-bis-06)
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Title               : RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs
Publication Date    : April 2007
Author(s)           : J. Sjoberg, M. Westerlund, A. Lakaniemi, Q. Xie
Category            : PROPOSED STANDARD
Source              : Audio/Video Transport
Area                : Real-time Applications and Infrastructure
Stream              : IETF
Verifying Party     : IESG